This invention relates generally to diagnosing neoplastic disease and, more specifically, to biomarkers that can be used to diagnose or determine a prognosis for prostate neoplastic disease, such as androgen-independent prostate cancer.
Cancer remains a major public health problem that profoundly affects the more than 1 million people diagnosed each year, as well as their families and friends. As our Nation's population grows and ages, more people will be diagnosed with cancer. Fortunately, the use of screening tests to detect cancers early often leads to more effective treatment with fewer side effects. Also, patients whose cancers are found early are less likely to die from their cancers than are those whose cancers are not found until symptoms appear.
Prostate cancer, which accounts for about 40 percent of all male cancers, is currently the most common type of cancer in American men and the second leading cause of cancer-related death in this population. An estimated 180,000 new cases of prostate cancer are diagnosed each year in the United States, and approximately 40,000 American men die of the disease annually.
Early stage prostate cancer is typically androgen-dependent, which means that the tumor cells require the hormone androgen to grow. A common strategy for treating this type of prostate cancer is androgen ablation therapy. The purpose of this therapy is to remove or reduce (ablate) the amount of androgen circulating in the individual to deprive cancer cells of this growth stimulating factor. When androgen ablation therapy is combined with traditional treatments, such as surgery or radiation therapy, most androgen-dependent prostate cancers are curable. However, some patients experience a relapse in prostate cancer that is refractory to the above treatment. These cancers are classified as androgen-independent and frequently become metastatic.
It is estimated that about 50% of all tumors considered to be localized in the prostate have already become metastatic and have escaped outside of the prostate. In many cases, such metastasized tumor cells, which are typically androgen-independent, are present in the patient at the time of diagnosis but are clinically undetectable. Difficulties in both detecting and treating late stage prostate cancers, such as androgen-independent prostate cancer, highlight the need for early detection.
Current methods for diagnosing prostate cancer are neither highly sensitive nor highly specific. Physical examination can miss small or centrally located tumors; serum prostate-specific antigen (PSA) determination detects both malignant and benign prostate disease; and sampling error in tissue biopsy may lead to erroneous benign diagnosis. At this time, other than PSA, few biomarkers specific for prostate cancer are in use, and no biomarkers specific for androgen-independent prostate cancer have been identified. This lack of biomarkers is unfortunate because improved early detection of prostate cancer can reduce mortality by improving chances for treating the cancer before it has spread.
Thus, there exists a need for identification of genes that can be used as diagnostic biomarkers and therapeutic targets for prostate cancer, such as androgen-independent prostate cancer. The present invention satisfies this need and provides related advantages as well.